Filter assemblies and systems for intake air for fuel cells

ABSTRACT

A filter assembly for removing particulate contaminants and chemical contaminants from an incoming dirty air stream for a fuel cell. The filter assembly also includes a noise suppression element that reduces sound waves or noise emanating from any equipment, such as a compressor. The filter assembly can include a particulate filter portion for removing physical or particulate contaminants, a chemical filter portion for removing chemical contaminants, or can have both portions.

This application is a continuation of U.S. patent application Ser. No.10/122,647, filed Apr. 10, 2002, now U.S. Pat. No. ______, which is acontinuation-in-part application of U.S. patent application Ser. No.09/879,441, filed Jun. 12, 2001, now U.S. Pat. No. 6,783,881, which is acontinuation-in-part application of U.S. patent application Ser. No.09/832,715, filed Apr. 11, 2001, now U.S. Pat. No. 6,780,534, all whichare incorporated herein by reference.

FIELD OF THE DISCLOSURE

The present disclosure is related to air filtering systems for removingparticulate and chemical contaminants from intake air. In particular,the disclosure is directed to a filter assembly that removes particulateand chemical contaminants from the intake air of fuel cells, and thatalso provides sound attenuation.

BACKGROUND OF THE DISCLOSURE

Practical and efficient generation of electrical energy has been soughtsince the discovery of electricity. Hydroelectric, fossil fuel andnuclear generation plants and batteries have long been used to supplyour electrical power needs. Power generation by use of fuel cells is arelatively recent development that is rapidly gaining acceptance forboth commercial and residential applications. As compared withconventional fossil fuel burning powered sources, they are relativelyclean and efficient. Fuel cells are electrochemical devices thatefficiently convert a fuel's chemical energy directly to electricalenergy. They chemically combine a fuel and oxidant without burning,thereby eliminating many inefficiencies and most pollution oftraditional combustion power systems.

A fuel cell operates in principle much like a battery. However, unlike abattery, a fuel cell does not run down or require recharging. It willcontinue to produce energy in the form of electricity and heat as longas fuel is supplied to it. In general, a fuel cell consists of twoelectrodes (an anode and a cathode) sandwiched around an electrolyte.For example, for a PEM fuel cell, hydrogen and oxygen are passed overthe anode and cathode electrodes respectively in a manner that generatesa voltage between the electrodes, creating electricity and heat, andproducing water as the primary byproduct. The hydrogen fuel is suppliedto the anode of the fuel cell. Some consume hydrogen directly, whileothers use a fuel reformer to extract the hydrogen from, for example, ahydrocarbon fuel such as natural gas, methanol, ethanol, or gasoline.Oxygen enters the fuel cell at the cathode. The oxygen can be suppliedin purified form or can come directly from atmospheric air.

The fuel cell uses a catalyst to cause the hydrogen atom to split into aproton and an electron, each of which takes a different path to thecathode. The protons pass through the electrolyte. The electrons createa useful electric current that can be used as an energy source, beforereturning to the anode where they are reunited with the hydrogen protonsand the oxygen to form water.

Fuel cells are generally characterized by the electrolyte material whichis sandwiched between the cathode and anode, and which serves as abridge for ion exchange. There are five main known types of fuel cells.Alkaline fuel cells (AFCs) contain a liquid alkaline electrolyte andhave been used primarily in space mission applications. Proton exchangemembrane fuel cells (PEMFCs) contain a solid polymer electrolyte. Theirlow temperature operation, high power density with the ability to varytheir output quickly to meet shifts in power demand make their use idealfor both mobile and stationary applications, such as powering vehiclesor buildings. Phosphoric acid fuel cells (PAFCs) utilize a phosphoricacid electrolyte and are currently used for commercial power generation.Molten carbonate fuel cells (MCFCs) contain a carbonate saltelectrolyte, which becomes molten at the operating temperature of about650° C. Solid oxide fuel cells (SOFCs) use a ceramic electrolytematerial and operate up to about 1000° C. Both the MCFCs and the SOFCscan use carbon monoxide as fuel.

Fuel cells have a vast range of potential applications. They can be usedto produce electricity for homes, businesses and industries throughstationary power plants. Fuel cells produce a direct current (dc) thatmust be inverted to alternating current for grid-connected applicationsor for use with most consumer products. However, future fuel cells couldbe operated in both grid-connected and non-grid-connected modes. Forresidential applications, smaller fuel cell power plants could beinstalled for the production of both heat and power. They could also beused to provide power to remote residential entities having no access toprimary grid power, potentially eliminating the necessity ofgrid-connections.

In addition to the larger scale power production applications, fuelcells could replace batteries that power consumer electronic productssuch as laptop computers, cellular phones and the like and could even bemicro-machined to provide power directly to computer chips. Anotherpromising commercial application of fuel cells is their potential toreplace the internal combustion engine in vehicle and transportationapplications. The applications for fuel cells are virtually unlimited.

All of the known fuel cell configurations discussed above have a commonneed for oxygen as an integral ingredient for performing the cell'schemical process. Other power sources, such as internal combustionengines, including diesel engines, also have a need for oxygen. For mostcommercial applications it is desirable for such oxygen to be supplieddirectly from the atmospheric air. However, it is accepted that intoday's world, all atmospheric air has some degree of contaminantspresent in it. Such contaminants can be relatively large such as loosedebris, insects, tree blossoms or the like, or can be in the nature ofsmall particulates suspended in the atmosphere such as dust, treepollen, smog or smoke particulates. Chemical contaminants are alsowidely present in atmospheric air, whether as a result of man-madepollution or as those which naturally occur. Typical chemicalcontaminants might include volatile organic compounds such as aromatichydrocarbons, methane, butane, propane and other hydrocarbons as well asammonia, oxides of nitrogen, ozone, smog, oxides of sulfur, carbonmonoxide, hydrogen sulfide, etc. Such contaminants may appearintentionally (such as in military environments or by terrorists) orunintentionally. Solution of the latter requirement becomes particularlyacute when the fuel cell is used in a mobile application that subjectsthe fuel cell to many varied atmospheric conditions.

Since efficient fuel cell operation depends on a delicately balancedchemical reaction, contaminants in the air used by the cell can have asignificant adverse effect on the cell's operation and, depending ontheir nature, can even cause the fuel cell to discontinue operation. Itis important therefore, that the fuel cell system include a filtrationsystem that is designed to eliminate harmful contaminants and one thatenables the fuel cell to be used in a wide range of use environments. Itis also important that other power generating equipment have afiltration system that is designed to eliminate harmful contaminants.

To obtain the amount of oxygen necessary for a fuel cell and otherequipment to produce the desired energy output, it has been founddesirable to pass the oxygen-bearing containing air through air movementequipment such as a compressor or fan located within the air flow streamsupplied to the fuel cell or other equipment. Unfortunately, typicalcompressors produce significant undesirable and annoying noise levels.It is desirable, therefore, in a power generating system to reduce andto minimize the noise produced by and/or transmitted through thecompressor and back into the environment. Since reduced system size isalso typically desirable, it is preferable that the filtration and soundattenuation features of the system be physically reduced as small aspossible and even preferably be combined within a single element orhousing. The present invention addresses the above-identified needs anddesires for an efficient and quiet system for use in a wide variety ofapplications, including fuel cell systems.

What is desired, therefore, is a power generator, such as a fuel cell,that functions within environments having a wide range of contaminants.

SUMMARY OF THE DISCLOSURE

The present invention provides filter assemblies for filtering theintake air used in power generating systems, such as with fuel cells.The present invention addresses a number of issues associated with thepractical implementation of fuel cell technology for power generation,whether that application is for generation of power in large stationaryapplications, vehicles, mobile lightweight equipment such as laptopcomputers or cell phones, or small stationary equipment such as radardetectors or sensors. These applications may draw less than 1 kW ofpower, or up to several megawatts of power. The filter assemblies of thepresent invention address the common need of generally all suchapplications, that is the need for a contaminant free supply of oxidantto the fuel cell, or at least a supply of oxidant having a reducedcontaminant level.

The amount and types of contaminants desirous to be removed from theintake air will depend on the amount and types of contaminants initiallypresent in the intake air (generally, the atmosphere or environmentsurrounding the fuel cell). The amount of contaminants and the type ofcontaminants present in the intake stream, prior to filtration, varieswidely depending on the location of the fuel cell, or at least thelocation of the air intake. For example, some environments have largelevels of particulate contamination such as dust, smog, smoke, orpollen, whereas other environments having large levels of chemicalcontaminants such as ammonia, carbon monoxide, sulfur dioxide, orsilicone. Generally, no two environments will have identical contaminantprofiles.

The amount and types of contaminants desirous to be removed from theintake air will also depend on the type of fuel cell. Any type of fuelcell or fuel cell stack can be used with the filter assemblies of thepresent invention, such as, for example, PEM fuel cells, solid oxidefuel cells, phosphoric acid fuel cells, and molten carbonate fuel cells.Typically, the higher temperature operating fuel cells, such as solidoxide fuel cells, can tolerate higher levels of organic contaminantsthan lower temperature operating fuel cells, such as PEM fuel cells.

Accordingly, one aspect of this invention is to provide filtration tothe intake air for a fuel cell system. The assemblies of the presentinvention provide particulate filtration and/or chemical filtration tothe incoming air stream to provide a purified oxidant supply. Since mostfuel cell system include some type of air moving equipment, such as acompressor, which can introduce contaminants into the air stream, thepresent invention also addresses filtration of air downstream of the airmoving equipment.

Unfortunately, air moving equipment typically produces loud noise inexchange for its air moving capabilities. It is the moving parts such asrotors, impellers, lobes, vanes, pistons and other various parts of airmoving equipment that create sound waves or noise in the frequencyranges of 3 Hertz to 30,000 Hertz, sometimes as high as 50,000 Hertz, atlevels of 85 to 135 dB at one meter. While not all the noise emanatingfrom the air moving equipment is objectionable, the various assembliesof the present invention are directed to reducing the most objectionableportions of the noise profiles.

In one particular embodiment, the invention is directed to a system forproducing power. The system comprises an air filter assembly thatcomprises a housing and a filter element in the housing. The housing hasan inlet and an outlet, the inlet accepting dirty atmospheric air to thefilter assembly, and the outlet providing clean air from the filterassembly. The filter element comprises at least a physical orparticulate filter portion to remove particulate contaminants from thedirty air. The filter element may also include a chemical filter portionto remove chemical contaminants from the dirty air. The filter assemblyalso includes a sound suppression or attenuation element, which may alsobe in the housing. The sound suppression element provides broadbandattenuation of the sound passing through the filter assembly. The airfilter assembly is operably connected to a power generation source, suchas a fuel cell.

The system generally also includes air moving equipment, such as acompressor or a blower, to provide enhanced air flow to the fuel cell.The filter assembly is also particularly arranged to reduce the level ofnoise emanating from any such equipment.

The present invention provides a filter assembly, the filter assemblyhaving a housing and a filter element in the housing. The housing has aninlet and an outlet, the inlet receiving dirty air into the filterassembly, and the outlet providing clean filtered air from the filterassembly. The filter assembly generally also has a sound suppressionelement, such as a resonator, sonic choke, full choke, sound adsorbentmaterial, that attenuates or otherwise reduces sound passing through thehousing by at least 3 dB at one meter, preferably by at least 6 dB.

The filter element can include a particulate filter portion, a chemicalfilter portion, and optionally a sound suppression element, all beingpart of the filter element. The sound suppression element providesbroadband sound attenuation of at least 6 dB at one meter. Theparticulate filter portion removes particulate contaminants from dirtyair entering the filter element, and the chemical filter portion, ifpresent, is removes chemical contaminants from the entering dirty air.The particulate filter portion can be positioned radially adjacent orforming a part of the sound suppression element. In some configurations,the particulate filter portion can be configured to providestraight-through flow.

Such a filter assembly or filter element can be used with any process orsystem that produces noise or sound and that benefits from cleanerintake gas (such as air). A fuel cell system is one power producingsystem with which filter assembly of the present invention can be used.Additionally, the filter assembly or filter element can be used withother power producing systems, such as diesel or gasoline engines.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic depiction of a power production system including afilter assembly of the present invention;

FIG. 2 is a front plan view of a first embodiment of the filter assemblyof FIG. 1, configured according to the principles of the presentinvention;

FIG. 3 is a fragmented cross-sectional perspective view of the filterassembly of FIG. 2;

FIG. 4 is a fragmented cross-sectional front plan view of the filterassembly of FIG. 3;

FIG. 5 is a perspective view of one embodiment of the filter elementportion of the filter assembly of FIGS. 3 and 4, configured according tothe principles of the present invention;

FIG. 6 is a schematic, perspective view of a portion of filter mediausable in the filter element of FIG. 5;

FIG. 7 is a fragmented cross-sectional view of the filter element ofFIG. 5, taken along line 5-5 of FIG. 5;

FIG. 8 is a perspective view of a second embodiment of a filter element,similar to that shown in FIG. 5, for use in the filter assembly of thepresent invention;

FIG. 9 is a fragmented cross-sectional view of a third embodiment of afilter element, similar to that shown in FIG. 7, for use in the filterassembly of the present invention;

FIG. 10 is a fragmented cross-sectional view of a fourth embodiment of afilter element, similar to that shown in FIGS. 7 and 9, for use in thefilter assembly of the present invention;

FIG. 11 is a graphical representation of sound attenuation versusfrequency for the filter assembly of FIGS. 3 and 4;

FIG. 12 is a fragmented cross-sectional front plan view of a secondembodiment of a filter assembly having an external configuration of thefilter assembly of FIG. 1;

FIG. 13 is a fragmented cross-sectional view of the chemical absorptionelement portion of the filter assembly of FIG. 12;

FIG. 14 is a right end view of an end cap of the chemical adsorptionelement of FIG. 13;

FIG. 15 is front plan view of one embodiment of an exhaust assembly ofFIG. 1, configured according to the principles of the present invention;

FIG. 16 is a cross-sectional view of the exhaust assembly of FIG. 15,taken along line 6-6 of FIG. 15;

FIG. 17 is a side plan view of a second embodiment of an exhaustassembly of FIG. 1, configured according to the principles of thepresent invention;

FIG. 18 is a front plan view of the exhaust assembly of FIG. 17;

FIG. 19 is a cross-sectional view of the exhaust assembly of FIGS. 17and 18 taken along line 19-19 of FIG. 18;

FIG. 20 is a cross sectional view of the exhaust assembly of FIGS. 17,18 and 19 taken along line 20-20 of FIG. 17;

FIG. 21 is a front plan view of a third embodiment of a filter assembly,configured according to the principles of the present invention;

FIG. 22 is a fragmented cross-sectional front plan view of the filterassembly of FIG. 21;

FIG. 23 is a cross-sectional view of the filter and noise suppressionelement, without the housing, of the filter assembly of FIGS. 21 and 22;

FIG. 24 is a cross-section view of the filter and noise suppressionelement similar to that of FIG. 23;

FIG. 25 is a graphical representation of sound attenuation versusfrequency for the filter assembly of FIGS. 21 through 24;

FIG. 26 is a perspective view of a small volume air handling system,comprising air handling equipment, an intake filter assembly and anexhaust filter assembly;

FIG. 27 is a fragmented cross-sectional perspective view of the intakefilter assembly of FIG. 26; and

FIG. 28 is a fragmented cross-sectional perspective view of the exhaustfilter assembly of FIG. 26.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the figures, wherein like numerals represent like partsthroughout the several views, there is schematically illustrated in FIG.1, a filter assembly 10 is shown in combination with an assembly ofequipment 101. One application for the filter assembly 10 of the presentinvention is to remove contaminants from air being used by equipment101. Another application of filter assembly 10 is to suppress noise orsound produced by and/or emanating from equipment 101.

As depicted in FIG. 1, atmospheric or ambient air 50 enters and isreceived by filter assembly 10 via an inlet 12. Prior to entering filterassembly 10, atmospheric air 50 generally contains various physical(e.g., particulate) and chemical contaminants and will be generallyreferred to herein as dirty air. Filter assembly 10 is constructed toremove various contaminants from dirty air 50 to provide clean air 54that exits from an outlet 14 of filter assembly 10. Clean air 54 is theintake air for equipment 101. In the embodiment depicted in FIG. 1,equipment 101 includes a fuel cell 102. Fuel cell 102 uses oxygen fromthe intake air 54, combined with a fuel source such as hydrogen (H₂) togenerate power. Water (H₂O) is a by-product of the oxygen and hydrogenreaction that occurs within fuel cell 102.

Filter assembly 10 of the present invention has at least one filterelement, schematically indicated at 15, for removing particulate and/orchemical contaminants. Filter element 15 has a dirty air intake side 13and a clean air outlet side 17. A housing 11 retains filter element 15therein. Inlet 12 is in fluid communication with dirty air intake side13, and housing outlet 14 is in fluid communication with clean air side17 of filter element 15. Housing 11 may be of varied configurations, andpreferably comprises at least two separable sections, so that access canbe gained to the contained filter element 15. The multiple sections canbe held together by latches, clamps, straps, or other suitable securingmechanisms. One preferred system for engaging two housing sections of afilter assembly could be that system disclosed in U.S. Pat. No.6,051,042 (Coulonvaux), which is incorporated herein by reference.Another preferred system is disclosed in U.S. Pat. No. 5,755,842 (Patelet al.), also incorporated herein by reference.

Atmospheric air 50 enters filter assembly 10 as dirty air through inlet12 in housing 11 and progresses to dirty air side 13 of filter element15. As the air passes through filter element 15 to its clean air side17, contaminants are removed by filter element 15 to provide filteredair. The filtered air, illustrated at 54, exits filter assembly 10through housing outlet 14 and is used by equipment 101. The type andextent of contaminants removed from the air to provide filtered air 54depends on the contaminants present in atmospheric air 50, theconfiguration of filter element 15, the type of fuel cell used, and thetemperature of the environment in which the fuel cell is operating.

Filter assembly 10 also includes a noise suppression element 19 toreduce or suppress the level of noise or sound emanating from equipment101 and passing back through filter assembly 10. Suppression element 19may be positioned within housing 11, and in some embodiments,suppression element 19 is defined by the configuration and shape ofhousing 11.

In order to facilitate or enhance the rate of chemical reaction within afuel cell, it is often desirable to introduce the oxygen bearing air 54to the fuel cell under pressure, or at a faster rate than would beavailable by simple “exposure” of the fuel cell to air at atmosphericpressure. A compressor or blower may be used for this purpose.Therefore, according to one configuration, equipment 101 includes acompressor 104 that provides air to fuel cell 102 for use in thecatalytic reaction. Compressor 104 is positioned upstream from fuel cell102. By the term “upstream”, it is meant that air flows from compressor104 to fuel cell 102; conversely, fuel cell 102 is positioned“downstream” from compressor 104. Filter assembly 10, which includesnoise suppression element 19, is also positioned upstream fromcompressor 104.

During operation of compressor 104, fast moving impellers, rotors orpistons generally present within compressor 104 emit sound, generallyreferred to as noise. This noise has a frequency that varies dependingon the type and configuration of the compressor, but is typically in therange of 3 Hertz to 30,000 Hertz, and sometimes as high as 50,000 Hertz,at a level of 85 to 135 dB at one meter. One particular type ofcompressor 104, a “Lysholm” twin screw compressor, available from OpconAutorotor AB of Sweden, operates at and provides a noise output in therange of about 160 to 1100 Hertz. Every compressor has a noise orfrequency distribution associated with its operation; this distributionwill depend on the type of compressor (including the specific model ofcompressor), and could depend on variants such as the input and outputflow rates, and environment temperature.

It is to be understood that such filter structures that will bedescribed are illustrative only of specific embodiments of suchstructures that embody the principles of this invention, and that thescope of the invention is not to be limited by specifics of theparticular described structures.

Noise from compressor 104 travels in any direction possible, such asdownstream to and through fuel cell 102 as well as upstream to andthrough filter assembly 10. Filter assembly 10, particularly by means ofits suppression element 19, reduces the level of sound travelingupstream from compressor 104 and out of the filter assembly intake 12 byat least 3 dB at one meter, typically by at least 6 dB, and preferablyby at least 25 dB. Various specific structures of filter assembly 10,including filter element 15 and noise suppression element 19, aredescribed below.

A First Embodiment of a Filter Assembly

A first example of a filter assembly configured according to theprinciples of this invention is shown in FIG. 2. For ease ofidentification, those elements in the embodiment of FIG. 2 that are thesame or which perform the same function as comparable elementspreviously discussed with respect to the diagrammatic representation ofFIG. 1 are followed by an alphabetic designation (i.e., “a”) in FIG. 2.The same will be used when describing further embodiments, such as theembodiment of FIG. 12, wherein the reference numerals are followed by analphabetic designation (i.e., “b”).

FIGS. 2 and 3 illustrate a filter assembly 10 a for use in a fuel celloperated passenger bus using a stack of PEM fuel cells providing anoverall power output of 200 kW. It should be understood that filterassembly 10 a is specifically designed for such an application, i.e., abus running on 200 kW, and that filter assemblies for otherapplications, such as, for example, other vehicles, stationary units, orportable electronic application, would be designed for thoseapplications that are different in size, shape and configuration, andoperating parameters without departing from the overall features offilter assembly 10 a.

The filter assembly view of FIG. 2 is illustrated as rotated about itscentral longitudinal axis, with respect to the illustration of FIG. 3,by 180 degrees. Filter assembly 10 a includes a generally cylindricalhousing 11 a which defines an air inlet 12 a and an air outlet 14 a.Dirty air 50 enters filter assembly 10 a via inlet 12 a, and clean air54 exits via outlet 14 a. The exterior of housing 11 a may includemounting brackets 31 a, 32 a for positioning and securing filterassembly 10 a in relation to surrounding equipment and structures. Asensor receptor port 35 a is present on the exterior of housing 11 aadjacent outlet 14 a. Filter housing 11 a may assume any number ofphysical shapes other that cylindrical; for example, filter assembly 10a may have a cross-sectional shape that is oval or obround, square,rectangular, or any other closed shape.

Housing 11 a can be made from any material that can be formed with thedesired elements, e.g., inlet 12 a, outlet 14 a, etc. Examples of usablematerials for housing 11 a include metals or plastics or other polymericmaterials. Typically, housing 11 a will be a thermoplastic or thermosetpolymeric material, such as epoxy, polycarbonate, polyethylene, and thelike. These materials may include reinforcement, such as a scrim orfibers, within the polymeric material to strength housing 11 a. In someembodiments it may be desired to avoid silicone mold release when makinghousing 11 a or any other part or element of filter element 110 a, assilicone fumes may be detrimental to the fuel cell. Alternately, it maybe possible to wash or otherwise cleanse housing 11 a to remove anycontaminants such as mold release.

Returning to the features of housing 11 a, receptor port 35 isconfigured to cooperatively receive a sensor that can monitorparameters, as desired, within the housing internal cavity. One exampleof a sensor that may be desired for use within sensor receptor port 35 ais an air mass flow sensor, generally referred to as a flow sensor or aflow meter. An air mass flow sensor can be used to monitor the mass ofair passing through outlet 14 a. The air mass passing through outlet 14a is directly related to the air mass passing through the entire system,including filter assembly 10 a and equipment 101 of FIG. 1 (such ascompressor 102, fuel cell 104, and optional exhaust apparatus 103). Bymonitoring any changes, specifically decreases, in air mass flow passingthrough filter assembly 10 a, the life of any physical or particulatefilter within filter assembly 10 a or any other equipment in the systemcan be estimated. Alternately, a sensor can be used to monitor the levelor accumulation of chemical contaminants that are passing through outlet14 a. By monitoring the amount of chemical contaminants passing throughoutlet 14 a, the remaining life of any chemical filter within filterassembly 10 a can be estimated.

One example of a preferred air mass flow sensor is a “hot wire” sensor,which uses the change in resistance through a wire to determine theamount of air passing over the wire. Such a hot wire sensor isavailable, for example, from TSI of St. Paul, Minn. Examples of devicesthat can monitor the accumulation or total contaminants include thosedisclosed in U.S. Pat. Nos. 5,976,467 and 6,187,596, both to Dallas etal. and incorporated herein by reference.

The various portions of filter assembly 10 a are illustrated in FIG. 3,where a cut-away view of filter assembly 10 a is provided. Operativelypositioned within housing 11 a are a filter element 15 a and a noisesuppression element 19 a.

Suppression element 19 a is configured to attenuate sound waves passingthrough the internal cavity defined by housing 11 a. In the preferredembodiment suppression element 19 a comprises a first resonator 21 and asecond resonator 22. In the preferred embodiment of the invention hereindescribed, first resonator 21 is configured to attenuate sound at a peakfrequency of about 900 Hz, and second resonator 22 is configured toattenuate sound at a peak frequency of about 550 Hz. Detailedinformation regarding sound suppression element 19 (FIG. 1), suppressionelement 19 a, and resonators 21, 22 hereinafter described in moredetail.

Specific characteristics of a preferred configuration of the filterassembly 10 a are illustrated in FIG. 4. Filter assembly 10 a,specifically housing 11 a, has a length “L” no greater than about 1500mm, preferably no greater than about 1000 mm. In one preferredembodiment, length “L” is no greater than 32 inches (813 mm) long.Filter assembly 10 a, which is generally cylindrical, has a diameter “D”no greater than about 18 inches (460 mm), preferably no greater thanabout 16 inches (406 mm). In the preferred embodiment, diameter “D” isno greater than 10 inches (254 mm). Length “L” and diameter “D” aregenerally dependent on the amount of volume allocated for occupation byfilter assembly 10 a within the system with which the filter assemblywill be used. Such system requirements may be dictated by the spacerequirements of the application with which the system will be employed.

Air flows into filter assembly 10 a via inlet 12 a, which has a diameter“D₁” of about 1 to 8 inches (25 to 203 mm). In the preferred embodiment,inlet diameter “D₁” is about 4 inches (102 mm). The length of inlet 12 a“L₁”, measured as the distance from the inlet end of housing 11 a toapproximately the dirty air side of filter element 15 a, is generallyabout 1 to 8 inches (25 to 203 mm). In the preferred embodiment, “L₁”¹is about 3.5 inches (90 mm). Outlet 14 a has a diameter “D_(O)” of about1 to 8 inches (25 to 203 mm). In the preferred embodiment, outletdiameter “D_(O)” is about 4 inches (102 mm).

Filter element 15 a occupies a volume within housing 11 a having alength “F” of about 4 to 8 inches (102 to 203 mm). The specific length“F” occupied by filter element 15 a will be conditioned on features suchas the type of filter element used, its filtering capabilities, thevolume of housing 11 a allotted to suppression element 19 a (FIG. 3),and the overall length “L” of housing 11 a. In the preferred embodiment,length “F” is about 7.3 inches (185 mm). Typically, the filter element15 a occupies the majority of the diameter D where filter element 15 ais positioned.

Noise suppression element 19 a occupies the majority of the remaininglength of housing 11 a. In the embodiment shown in FIGS. 3 and 4,suppression element 19 a comprises a first resonator 21 and a secondresonator 22. First resonator 21 occupies a length “R₁ “of about 6.4inches (163 mm) and second resonator 22 occupies a length “R₂” of about12.2 inches (310 mm). The number of resonators used and the specificlengths (e.g., R₁ and R₂) occupied by the resonators are a function ofthe desired sound attenuating properties of the resonator. That is, thefrequency of the sound attenuated by the resonators is dependent on theconfiguration of the resonators, specifically, the volume occupied. Asstated, additional information regarding sound attenuation andresonators is provided below.

Mounting brackets 31 a, 32 a on the exterior of filter assembly 10 a arespaced apart 18.5 inches (470 mm), which is designated by “L_(B)”. Firstmounting bracket 31 a is spaced 8.9 inches (227 mm) from inlet 12 a,designated by “L_(A)”. It is understood that the positioning of anymounting brackets is dependant on the overall length “L” of filterassembly 10 a, its desired positioning in respect to surroundingequipment or structures, and positioning of internal baffles or otherstructure within housing 11 a.

Physical or Particulate Removal Portion of the Filter Assembly

Filter assembly 10 of the present invention, in particular filterelement 15, includes a portion for removing physical contaminants suchas particulates from the incoming air 50. It is understood that largeitems, such as leaves, birds, rodents and other debris, will be removedby a screen, mesh, separator or the like from incoming atmospheric air50 prior to the air reaching filter assembly 10. A water or liquidseparator may be included to remove water or fluid from air 50 prior toentering filter assembly 10 as is known in the art.

A series of particulate removal portions may be used within filterassembly 10, with each subsequent particulate removal portion removing asmaller sized particle. Alternately, a single particulate removalportion can be used.

Typically, the particulate removal portion contains a filter media, suchas a fibrous mat or web, including cellulosic materials, to removeparticles. Examples of particulates or particles removed by aparticulate removal portion include dust, dirt, pollen, dieselparticulate, insects, wood chips and sawdust, metal shavings, cosmicdust, and the like. Some particulates may be doubly harmful to theoperation of the fuel cell, both as the physical particle and themolecular structure of the particle; for example, limestone, is a basicmaterial that could harm the electrolyte in a PEM fuel cell, which isacidic. Other types of fuel cells may be detrimentally affected byacidic contaminants. Heavy hydrocarbons, particularly those found inroad tar, can also detrimentally affect operation of a fuel cell.

The filter media can be treated in any number of ways to improve itsefficiency in removing minute particulates; for example,electrostatically treated media can be used, as can cellulose orsynthetic media or a combination thereof, having one or more layers ofnanofiber, or other types of media known to those skilled in the art.For details regarding types of nanofiber that could be used, see forexample, U.S. Pat. No. 4,650,506 (Barris et al.), which is incorporatedherein by reference.

It is understood that any number of particulate removal portions havingany combination of particulate removal efficiency can be used. Thedesired particulate removal system will depend on the type, size andnature of contaminants present in the atmosphere (for example, leaves,cottonwood blossoms, lint, snow, cosmic dust, etc.) and the desiredcleanliness level of the resulting filtered air. The media used infilter element 15 can vary, depending on the particulate removalefficiency desired, the maximum level of acceptable pressure dropthrough filter element 15, and other such factors.

Filter element 15 a of FIGS. 3 and 4 is illustrated in more detail inFIG. 5. In the preferred embodiment, filter element 15 a includes filtermedia 55 that is wound about a central axis to form a cylindricallyshaped filter element. The filter element includes a sealing systemgenerally indicated at 60. One preferred sealing system is disclosed,for example, in U.S. Pat. No. 4,720,292, which is incorporated herein byreference.

In preferred constructions, filter media 55 is designed to removeparticulate from air passing through the filter media 55, while thesealing system 60 is designed to provide a seal between filter element15 a and the interior sidewalls of housing 11 a, as shown in FIGS. 3 and4. By the term “seal,” it is meant that sealing system 60, under normalconditions, prevents unintended levels of air from passing through aregion between the outer surface of filter element 15 a and the interiorsidewall of housing 11 a; that is, sealing system 60 inhibits air flowfrom avoiding passage through filtering media 55 of filter element 15 a.

In certain preferred arrangements, filter media 55 is configured forstraight-through flow. By “straight-through flow,” it is meant thatfilter media 55 is configured so as to have a first flow face 105(corresponding to an inlet end, in the illustrated embodiment) and anopposite, second flow face 110 (corresponding to an outlet end, in theillustrated embodiment). Straight-through flow is often desired becausea straight-through flow filter can handle greater amounts of air passingtherethrough compared to, for example, a pleated filter. It is intendedthat there is no distinction between “straight-though flow” and “in-lineflow”. Air enters in one direction 114 through first flow face 105 andexits in the same direction 116 from second flow face 110. In thisembodiment, first flow face 105 correlates to dirty air side 13 of thefilter element of FIG. 1 and second flow face 110 correlates to cleanair side 17 of the filter element of FIG. 1.

When filter element 15 a is used with an in-line flow housing such ashousing 11 a of FIGS. 3 and 4, in general, the air will enter throughinlet 12 a of housing 11 a in one direction, enter filter element 15 athrough first flow face 105 in the same direction, exit filter element15 a in the same direction from second flow face 110, and exit housing11 a through outlet 14 a also in the same direction.

Although first flow face 10S is described above as corresponding to aninlet end (and dirty air side 13), and second flow face 110 is describedabove as corresponding to an outlet end (and clean air side 17), theinlet and outlet ends (and dirty air side and clean air side) can bereversed. That is, first flow face 105 depicted in FIG. 5 can correspondto an outlet end, while second flow face 110 depicted in FIG. 5 cancorrespond to an inlet end. In other words, the physical orientation offilter element 15 a relative to the direction of air flow therethroughcould be reversed.

In FIG. 5, first flow face 105 and second flow face 110 are depicted asplanar and as parallel to one another. In other embodiments, first flowface 105 and second flow face 110 can be non-planar, for example,frusto-conical. Further, first flow face 105 and second flow face 110need not be parallel to each other.

In the preferred embodiment, the media of filter element 15 a is a woundor rolled construction. That is, filter element 15 a will typicallyinclude a layer of filter media that is wound completely or repeatedlyabout a central axis. Typically, the wound construction will be a coil,in that a layer of filter media will be rolled in a series of turnsaround a central axis. In arrangements where a wound, coiledconstruction is used, filter element 15 a will be in the shape of a rollof filter media, typically permeable fluted filter media.

Attention is now directed to FIG. 6, where a schematic, perspective viewdemonstrating the principles of operation of certain preferred mediausable in the filter constructions herein is illustrated. In FIG. 6, afluted media construction is generally designated at 122. Preferably,fluted construction 122 includes a layer 123 of corrugations having aplurality of flutes 124 and a face sheet 132. The FIG. 6 embodimentshows two sections of face sheet 132, at 132A (depicted on top ofcorrugated layer 123) and at 132B (depicted below corrugated layer 123).Typically, the preferred media construction 125 used in arrangementsdescribed herein will include corrugated layer 123 secured to bottomface sheet 132B. When using this media construction 125 in a rolledconstruction, it typically will be wound around itself, such that bottomface sheet 132B will cover the top of corrugated layer 123. Face sheet132 covering the top of corrugated layer 123 is depicted as 132A. Itshould be understood that in a “rolled” media configuration face sheet132A and 132B are the same sheet 132.

When using this type of media construction 125, flute chambers 124preferably form alternating peaks 126 and troughs 128. Peaks 126 andtroughs 128 divide flutes 124 into an upper row and lower row. In theparticular configuration shown in FIG. 6, the upper flutes form flutechambers 136 closed at the downstream end, while flute chambers 134having their upstream end closed form the lower row of flutes. Flutedchambers 134 are closed by a first end bead 138 that fills a portion ofthe upstream end of the flute between fluting sheet 130 and secondfacing sheet 132B. Similarly, a second end bead 140 closes thedownstream end of alternating flutes 136. In some preferred systems,both first end bead 138 and second end bead 140 are straight along allportions of the media construction 125, never deviating from a straightpath. In some preferred systems, first end bead 138 is both straight andnever deviates from a position at or near one of the ends of mediaconstruction 125, while second end bead 140 is both straight and neverdeviates from a position at or near one of the ends of mediaconstruction 125. Flutes 124, face sheet 132, and end beads 138, 140provide media construction 125 that can be formed into filter element 15a.

When using media constructed in the form of media construction 125,during use, unfiltered air enters flute chambers 136 as indicated by theshaded arrows 144. Flute chambers 136 have their upstream ends 146 open.The unfiltered fluid flow is not permitted to pass through downstreamends 148 of flute chambers 136 because their downstream ends 148 areclosed by second end bead 140. Therefore, the air is forced to proceedthrough fluting sheet 130 or face sheets 132. As the unfiltered airpasses through fluting sheet 130 or face sheets 132, the air is cleanedor filtered. The cleaned air is indicated by the unshaded arrow 150. Theair then passes through flute chambers 134 (which have their upstreamends 151 closed) to flow through the open downstream end 152 (FIG. 5)out fluted construction 122. With the configuration shown, theunfiltered air can flow through fluted sheet 130, upper facing sheet132A, or lower facing sheet 132B, and into a flute chamber 134.

Typically, media construction 125 will be prepared and then wound toform a rolled construction 100 of filter media. When this type of mediais selected for use, media construction 125 includes corrugated layer123 secured with end bead 138 to bottom face sheet 132B (as shown inFIG. 6, but without top face sheet 132A). In these types ofarrangements, media construction 125 will include a leading edge at oneend and a trailing edge at the opposite end, with a top lateral edge anda bottom lateral edge extending between the leading and trailing edges.By the term “leading edge”, it is meant the edge that will be initiallyturned or rolled, such that it is at or adjacent to the center or coreof the rolled construction. The “trailing edge” will be the edge on theoutside of the rolled construction, upon completion of the turning orcoiling process.

The leading edge and the trailing edge should be sealed betweencorrugated sheet 123 and bottom face sheet 132B, before winding thesheet into a coil, in these types of media constructions 125. While anumber of ways are possible, in certain methods, the seal at the leadingedge is formed as follows: (a) corrugated sheet 123 and bottom facesheet 132B are cut or sliced along a line or path extending from the toplateral edge to the bottom lateral edge (or, from the bottom lateraledge to the top lateral edge) along a flute 124 forming a peak 126 atthe highest point (or apex) of peak 126; and (b) sealant is appliedbetween bottom face sheet 132B and corrugated sheet 123 along the lineor path of cut. The seal at the trailing edge can be formed analogouslyto the process of forming the seal at the leading edge. While a numberof different types of sealant may be used for forming these seals, oneusable material is a non-foamed sealant available from H.B. Fuller, St.Paul, Minn.

When using media construction 125, it may be desired by the systemdesigner to wind the construction 125 into a rolled construction offilter media, such as filter element 15 a of FIG. 5. A variety oftechniques can be used to coil or roll the media. It can be appreciatedthat non-round center winding members may be utilized for making otherfiltering media shapes, such as filter media having an oblong orobround, oval, rectangular, or racetrack-shaped profile.

Media construction 125 can also be wound without a mandrel or centercore. One method of forming a coreless rolled construction is asfollows: (a) troughs 128 of the first few corrugations of corrugatedsheet 123 spaced from the leading edge are scored from the top lateraledge to the bottom lateral edge (or from the bottom lateral edge to thetop lateral edge) to help in rolling construction 125; for example, thefirst four corrugations from the leading edge will have a score line cutalong troughs 128; (b) bead 140 of sealant is applied along the top ofcorrugated sheet 123 along the lateral edge opposite from the lateraledge having end bead 138; (c) the leading edge is initially turned orrolled over against itself and then pinched together to be sealed withsealant bead 140; and (d) the remaining corrugated sheet 123 havingbottom face sheet 132B secured thereto is coiled or rolled or turnedaround the pinched leading edge.

In other methods, coreless constructions can be made from mediaconstruction 125 by automated processes, as described in U.S. Pat. Nos.5,543,007 and 5,435,870, each incorporated by reference herein. In stillother methods, the media construction can be rolled by hand.

When using rolled constructions such as filter construction 100, thesystem designer will want to ensure that the outside periphery ofconstruction 100 is closed or locked in place to prevent filterconstruction 100 from unwinding. There are a variety of ways toaccomplish this. In some applications, the outside periphery is wrappedwith a periphery layer. The periphery layer can be a non-porous,adhesive material, such as plastic with an adhesive on one side. Whenthis type of layer is utilized, the periphery layer prevents filterconstruction 100 from unwinding and prevents air from passing throughthe outside periphery of filter construction 100, maintainingstraight-through flow through filter construction 100.

In some applications, filter construction 100 is secured in its rolledconstruction by sealing the trailing edge of media construction 125 withan adhesive or sealant along a line 160 (FIG. 5) to secure the trailingedge to the outside surface of filter construction 100. For example, abead of hot-melt may be applied along line 160.

Additionally or alternatively, a support band 162 can be provided aroundthe outer perimeter of filter construction 100 to secure the trailingedge. In FIG. 5, support band 162 is shown positioned at first flow face105.

Filter element 15 a includes an end frame 200 positioned at second flowface 110. A cross-sectional fragmented view of filter element 15 a isshown in FIG. 7; filter construction 100, with its various features, isshown in phantom. Referring to both FIGS. 5 and 7, frame 200 includes anouter annular peripheral band 205 and radial cross-braces 210.Cross-braces 210 extend inwardly from the outer peripheral band orcollar 205 and meet at center 215 on the axis of the filter element. Thecrossbraces define an annular recessed seat portion when they meet atthe center 215 of the frame 200. Peripheral band 205 extends along theouter perimeter of filter construction 100 at second flow face 110 andextends longitudinally distally away from second flow face 110. In theparticular embodiment shown in FIGS. 5 and 7, frame 200 includes asecond inner annular ring 212 that intersects and connects to thecross-braces 210.

End frame 200 supports sealing system 60 and provides a solid,relatively non-deformable surface to facilitate the seal between thefilter element and filter housing formed by sealing system 60. Inparticular, sealing system 60 comprises an annular ring of round sealantmaterial that is mounted to and seated on the distal portion ofperipheral band 205 that projects outwardly from second flow face 110.Sealing system 60 is preferably a compressible material, such as apolyurethane foam material, that is configured to cooperatively engagethe interior sidewalls of housing 11 a and provide an air-tight seal.Sealing system 60 can have a stepped cross-sectional configuration ofdecreasing outermost diameter dimensions to facilitate sealing and toensure a tight seal.

In general, for a properly functioning radially sealing structure, thecompressible sealing system 60 needs to be compressed when filterelement 15 a is operatively mounted in housing 11 a. In many preferredconstructions, it is compressed about 15% to 40% (often about 20 to 33%)of its thickness, at the thickest portion thereof, to provide for astrong robust seal yet still be one that can result from handinstallation of the element with forces on the order of 80 pounds orless, preferably 50 pounds or less, and generally from about 20-40pounds.

A second embodiment of a filter element for use in the filter assemblyof the present invention is illustrated in FIG. 8 as filter element 15b. Filter element 15 b is similar to filter element 15 a of FIGS. 5 and7, except that frame 200 of filter element 15 b does not include innerannular ring 212.

Additional details regarding filter element 15 a, filter element 15 b,and other usable filter elements can be found in U.S. Pat. No.6,190,432, which is incorporated herein by reference.

It is understood that other filter constructions, other than thosehaving straight-through flow, can be used. Examples of other particulatefilter constructions that can be used include pleated media filters,panel filters, filters having a volume of depth media, and the like.

A Chemical Removal Portion of the Filter Assembly

Referring again to FIG. 1, filter assembly 10 preferably also includes aportion designed to remove contaminants from the atmosphere by eitheradsorption or absorption. As used herein, the terms “adsorb”,“adsorption”, “adsorbent” and the like, are intended to also include themechanisms of absorption and adsorption.

The chemical removal portion typically includes a physisorbent orchemisorbent material, such as, for example, desiccants (i.e., materialsthat adsorb or absorb water or water vapor) or materials that adsorb orabsorb volatile organic compounds and/or acid gases and/or basic gases.The terms “adsorbent material,” “adsorption material,” “adsorptivematerial,” “absorbent material,” absorption material,” absorptivematerial,” and any variations thereof, are intended to cover anymaterial that removes chemical contaminants by adsorption or absorption.Suitable adsorbent materials include, for example, activated carbon,activated carbon fibers, impregnated carbon, activated alumina,molecular sieves, ion-exchange resins, ion-exchange fibers, silica gel,alumina, and silica. Any of these materials can be combined with, coatedwith, or impregnated with materials such as, for example, potassiumpermanganate, calcium carbonate, potassium carbonate, sodium carbonate,calcium sulfate, citric acid, phosphoric acid, other acidic materials,or mixtures thereof. In some embodiments, the adsorbent material can becombined or impregnated with a second material.

The adsorbent material typically includes particulates or granulatedmaterial and can be present in varied configurations, for example, asgranules, beads, fibers, fine powders, nanostructures, nanotubes,aerogels, or can be present as a coating on a base material such as aceramic bead, monolithic structures, paper media, or metallic surface.Typically, the adsorbent materials, especially particulate or granulatedmaterials, are provided as a bed of material.

Alternately, the adsorbent material can be shaped into a monolithic orunitary form, such as, for example, a large tablet, granule, bead, orpleatable or honeycomb structure that optionally can be further shaped.In at least some instances, the shaped adsorbent material substantiallyretains its shape during the normal or expected lifetime of the filterassembly. The shaped adsorbent material can be formed from afree-flowing particulate material combined with a solid or liquid binderthat is then shaped into a non-free-flowing article. The shapedadsorbent material can be formed by, for example, a molding, acompression molding, or an extrusion process. Shaped adsorbent articlesare taught, for example, in U.S. Pat. Nos. 5,189,092 (Koslow), and5,331,037 (Koslow), which are incorporated herein by reference.

The binder used for providing shaped articles can be dry, that is, inpowdered and/or granular form, or the binder can be a liquid, solvated,or dispersed binder. Certain binders, such as moisture curable urethanesand materials typically referred to as “hot melts”, can be applieddirectly to the adsorbent material by, for example, a spray process. Insome embodiments, a temporary liquid binder, including a solvent ordispersant which can be removed during the molding process, is used.Suitable binders include, for example, latex, microcrystallinecellulose, polyvinyl alcohol, ethylene-vinyl acetate, starch,carboxylmethyl cellulose, polyvinylpyrrolidone, dicalcium phosphatedihydrate, and sodium silicate. Preferably the composition of a shapedmaterial includes at least about 70%, by weight, and typically not morethan about 98%, by weight, adsorbent material. In some instances, theshaped adsorbent includes 85 to 95%, preferably, approximately 90%, byweight, adsorbent material. The shaped adsorbent typically includes notless than about 2%, by weight, binder and not more than about 30%, byweight, binder.

Another embodiment of a suitable adsorbent material for use in thechemical removal portion is an adsorbent material that includes acarrier. For example, a mesh or scrim can be used to hold the adsorbentmaterial and binder. Polyester and other suitable materials can be usedas the mesh or scrim. Typically, any carrier is not more than about 50%of the weight of the adsorbent material, and is more often about 20 to40% of the total adsorbent weight. The amount of binder in the shapedadsorbed article with the carrier typically ranges about 10 to 50% ofthe total adsorbent weight and the amount of adsorbent materialtypically ranges about 20 to 60% of the total adsorbent weight.

The chemical removal portion can include strongly basic materials forthe removal of acid contaminants from the air, or strongly acidicmaterials for the removal of basic contaminants from the air, or both.Preferably, the basic materials and acidic materials are sufficientlyseparated from each other so that they do not interact with or canceleach other. In some embodiments, the adsorbent material itself may bethe strongly acidic or strong basic material. Examples of such materialsinclude materials such as polymer particulates, activated carbon media,zeolites, clays, silica gels, and metal oxides. In other embodiments,the strongly acidic materials and the strongly basic materials can beprovided as surface coatings on carriers such as granular particulate,beads, fibers, cellulosic material, fine powders, nanotubes, andaerogels. Alternately or additionally, the acidic and basic materialthat forms the acidic and basic surfaces may be present throughout atleast a portion of the carrier; this can be done, for example, bycoating or impregnating the carrier material with the acidic or basicmaterial.

Examples of acidic compounds that are often present in atmospheric airand are considered as contaminants for fuel cells include, for example,sulfur oxides, nitrogen oxides, hydrogen sulfide, hydrogen chloride, andvolatile organic acids and nonvolatile organic acids. Examples of basiccompounds that are often present in atmospheric air and are consideredas contaminants for fuel cells include, for example, ammonia, amines,amides, sodium hydroxides, lithium hydroxides, potassium hydroxides,volatile organic bases and nonvolatile organic bases.

For PEM fuel cells, the cathodic reaction occurs under acidicconditions, thus, it is undesirable to have basic contaminants present.An example of a preferred material for removing basic contaminants, suchas ammonia, is activated carbon impregnated or coated with citric acid.

A first embodiment of a filter element 15 (FIG. 1) having both thephysical or particulate removal portion and a chemical removal portionis shown in FIG. 9 as filter element 15 c. Filter element 15 c issimilar to filter element 15 a of FIG. 7 in that filter element 15 c hasfilter construction 100 (shown in phantom in FIG. 9) with first flowface 105 and second flow face 110, support band 162, frame 200, andsealing system 60. Filter element 15 c further includes an adsorbentelement 300, such as shaped activated carbon. Adsorbent element 300 ispositioned on frame 200 within frame 200 and sealing system 60. Thecompressible sealing system 60 frictionally retains adsorbent element300 in the desired position, but can be deformed to release adsorbentelement 300 for replacement when the adsorbent is spent.

In a preferred embodiment, adsorbent element 300 is a shaped mass ofactivated carbon material held together by a thermoplastic binder. Apreferred adsorbent element 300 includes activated carbon material,sieve size 12×20 or 8×16, molded with a level of 8% ethylene-vinylacetate binder. Such a preferred adsorbent element 300 can be made inaccordance with the teachings of U.S. Pat. Nos. 5,189,092 (Koslow) or5,331,037 (Koslow). In another preferred embodiment, adsorbent element300 is made from layers (not shown) of carbon material available fromHollingsworth & Vose of East Walpole, Mass. (also known as H&V).

In the embodiment shown, adsorbent element 300 is positioned adjacentsecond flow face 110; thus air flowing through filter element 15 c wouldenter filter construction 100 via first flow face 105 and exit viasecond flow face 110, and then pass through adsorbent element 300. Sucha configuration has adsorbent element 300 “downstream” of theparticulate removing filter construction 100. All air passing throughfilter construction 100 preferably passes through adsorbent element 300.It is understood that adsorbent element 300 could alternatively bepositioned “upstream” from filter construction 100.

A second embodiment of a filter element 15 (FIG. 1) having both thephysical or particulate removal portion and a chemical removal portionis shown in FIG. 10 as filter element 15 d. Filter element 15 d issimilar to filter element 15 a in that filter element 15 d has filterconstruction 100 (shown in phantom) with first flow face 105 and secondflow face 110, support band 162, frame 200, and sealing system 60.Filter element 15 d further includes the adsorbent element 300, exceptthat adsorbent element 300 is positioned between second flow face 110and cross-braces 210 of frame 200. Peripheral band 205 (see FIG. 8) offrame 200 holds absorbent 300 against second flow face 110. Adsorbentelement 300 may be permanently affixed to one or each of frame 200 andfilter construction 100, or may be disengageable therefrom. Again, allair passing through second flow face 110 of filter construction 100preferably also passes through adsorbent element 300.

In filter elements 15 c and 15 d, the chemical removal portion,specifically adsorbent element 300, has been combined with theparticulate removal portion to form a single structure. It is understoodthat in some embodiments, the chemical removal portion will be separateand spaced from the particulate removal portion. It is furtherunderstood that the particulate removal portion and chemical removalportion can be combined in a single element that removes both physicaland chemical contaminants. In one example, the filter media of aparticulate removal portion can be made with fibers that have a surfacetreatment capable of chemisorbing or otherwise reacting or interactingwith acidic or basic contaminants, thus providing a chemical removalportion. In another example, a bed of activated carbon granules can bearranged and configured to remove physical contaminants from the air ifthe spacing between the granules is sufficiently small.

One preferred filter element that includes both particulate and chemicalremoval portions is disclosed in U.S. Pat. No. 6,152,996 (Linnersten etal.), which is incorporated herein by reference.

Additional information regarding chemical removal portions of filterelements for use with fuel cell systems is disclosed in U.S. Pat. No.6,432,177, which is incorporated herein by reference in its entirety.

A Sound Suppression Element of the Filter Assembly

Referring again to FIG. 1, filter assembly 10 of the present inventionincludes a noise or sound suppression element 19 to reduce or suppressthe level of noise or sound emanating from equipment 101. Such noisereduction is preferably at least 3 dB at one meter, typically at least 6dB, preferably at least 10 dB, and most preferably at least 25 dB. Thecatalytic reaction occurring within fuel cell 102 is a silent process,in that the hydrogen fuel, the reaction at the cathode, and theproduction of power, produce no sound audible by humans. Detailsregarding the construction and operation of fuel cells 102 are providedbelow. However, although fuel cell 102 is silent, the equipment ormachinery often used to provide an increased flow of air to fuel cell102, such as compressor 104 of FIG. 1, generally produce significantnoise. Air moving equipment that may be used in conjunction with fuelcell 102 includes compressors, fans, blowers, and pumps.

Sound emanating from equipment such as compressor 104 will travel in anydirection as permitted by the fuel cell, equipment and filterassemblies. That is, sound would travel upstream from the compressor,against the flow of the air, to filter assembly 10; and sound wouldtravel downstream to fuel cell 102. In accordance with the presentinvention, filter assembly 10 reduces the noise emanating fromcompressor 104 through the filter assembly and out to the surroundingenvironment, by attenuating the sound with sound suppression element 19of filter assembly 10.

Sound suppression element 19 can be any type of element that, togetherwith other features of filter assembly 10 that may attenuate orotherwise reduce the sound, provides reduction in the sound by at least3 dB, typically at least 6 dB, preferably by at least 10 dB, and morepreferably by at least 25 dB. Examples of sound suppression elements 19include mufflers, lined ducts, baffles, bends in the sound path,plenums, expansion chambers, resonators, sonic chokes, full chokes,sound adsorptive material, and various combinations thereof. Variousdetails regarding sound suppression elements are disclosed, for example,in U.S. Pat. No. 6,082,487 (Angelo et al.), which in incorporated hereinby reference.

Certain typical suppression elements 19 include an outer wall, usuallycylindrical, defining an internal volume, and an inlet and outlet tubeoriented within the internal volume of the outer wall. It is preferredthat the outer wall and any other structures have minimal surfaces thatare planar or flat; rather, it is preferred that the surfaces ofsuppression element 19 are curved, to reduce the amount of vibration ordrumming that often occurs with flat walls. In typical arrangements, theoutlet tube defines a sonic choke. An inner, perforated wall is spacedfrom the outer wall, to define an annular volume therebetween. Theannular volume may include a packing or padding of absorptive materialwithin the annular volume. This absorptive material within the annularvolume provides an absorptive function, and also helps reduce drummingof the outer wall or shell. In certain arrangements, the innerperforated wall and annular volume are in aligmnent with the inletregion of suppression element 19. That is, the inner perforated wall maycircumscribe at least a portion of the inlet tube.

A preferred suppression element 19 is a resonator. A resonator is anenclosed volume of air in communication with the exterior through asmall opening. The enclosed air resonates at a finite range offrequency. This range of frequency and the level of attenuation dependon the dimensions of the enclosed volume. The frequency resonated withinthe enclosed volume determines the noise frequency attenuated by theresonator.

In filter assembly 10 a illustrated in FIGS. 3 and 4, suppressionelement 19 a comprises first resonator 21 and second resonator 22.Notice that first resonator 21 is positioned adjacent outlet 14 a andsecond resonator 22 is positioned upstream or closer to inlet 12 a. Suchdesignated “first” and “second” positioning of the resonators has beenselected because noise from equipment 101 (FIG. 1) would be movingupstream (opposite to the direction of air flow) through filter assembly10 a from outlet 14 a to inlet 12 a. First and second resonators 21, 22can be designed to attenuate the same or a different range of soundfrequencies. Generally, if resonators 21, 22 remove the same range ofnoise frequency, the level of noise decrease will be greater. Ifresonators 21, 22 remove noise of different frequency ranges, theoverall ranges of frequencies attenuated will be greater.

In one preferred embodiment, first resonator 21 is designed to attenuatesound at a peak frequency of about 900 Hz, and second resonator 22 isdesigned to attenuate sound waves at a peak frequency of about 550 Hz.As illustrated in FIGS. 3 and 4, various features differ between firstresonator 21 and second resonator 22. For example, the volume occupiedby second resonator 22 is much greater that that occupied by firstresonator 21. The volume of first resonator 21 is generally defined bythe interior walls of housing 11 a between outlet 14 a and an internalannular baffle 25 a. The volume occupied by second resonator 22 isgenerally defined by the interior walls of housing 11 a between internalbaffle 25 a and flow face 110 (FIG. 5) of the filter element.Additionally, the perforations within a central wall structure 28 varybetween first resonator 21 and second resonator 22. For example, theshape and size of the apertures, the spacing between adjacent apertures,and their orientation differ between the two resonators. These variousfeatures of each resonator dictate the frequencies attenuated thereby.Design of resonators for desired frequency attenuation is well known inthe art of sound suppression and attenuation and will not be detailedherein.

Additionally, first and second resonators 21, 22 are spacedapproximately 3 inches (76 mm) apart, as measured by the longitudinalspacing between the perforations in central wall structure 28 of the tworesonators. This distance between resonators 21, 22, designated at 24 inFIG. 4, will attenuate sound having a frequency whose ¼ wavelength isequal to this distance. A distance of approximately 3 inches (76 mm)provides a peak attenuation of about 1100 Hz.

FIG. 11 graphically illustrates the levels and frequencies of soundattenuated by the preferred embodiment described above. First resonator21 attenuates sound at a peak frequency of about 900 Hz, secondresonator 22 attenuates sound at a peak frequency of about 550 Hz, andthe ¼ wavelength spacing 24 attenuates sound at about 1100 Hz. Thecomposite sound attenuation of the three spans the fundamentalfrequencies of a typically twin-screw compressor, such as the 160 1100Hz of a Lysholm twin screw compressor manufactured by Opcon.

Referring again to FIG. 1, suppression element 19 may be positionedwithin housing 11, and in some embodiments, suppression element 19 isdefined by housing 11. In the embodiment of filter assembly 10 a, firstand second resonators 21, 22 are partially defined by housing 11 a. Theinterior walls of housing 11 a together with internal baffle 25, definethe volume occupied by resonators 21, 22.

Various other features of housing 11 a may provide sound attenuation.For example, inlet 12 a, as illustrated in FIG. 4, has a bell shapedexpansion in the axial direction from a 4 inch (102 mm) to 10 inch (254mm) diameter. This expansion provides a broadband sound attenuation ofapproximately 3 dB.

It is noted that filter element 15, such as any of filter elements 15 a,15 b, 15 c, 15 d, may have additional sound attenuation propertiesassociated with the particulate removal portion or the chemical removalportion. For example, filter construction 100 (FIGS. 5 and 7), mayattenuate some frequencies a low amount, such as 1 dB. Additionally,adsorbent element 300 (FIGS. 9 and 10) may attenuate some frequencies.It has been found that various shaped adsorbent elements, such as thosetaught by U.S. Pat. Nos. 5,189,092 (Koslow), and 5,331,037 (Koslow),provide some sound attenuation; the frequency attenuated and the level(i.e., dB) will depend on the specific features of the shaped adsorbentelement.

A Second Embodiment of a Filter Assembly

A second example of a filter assembly is shown in fragmentedcross-section in FIG. 12 as a filter assembly 10 b. Similar to filterassembly 10 a, filter assembly 10 b is for use in a fuel cell operatedpassenger bus using a stack of PEM fuel cells providing an overall poweroutput of 200 kW. It should be understood that filter assembly 10 b isspecifically designed for such an application, (i.e., a bus running on200 kW), and that filter assemblies for other applications would bedesigned for those applications that are different in size, shape andconfiguration, without departing from the overall features of filterassembly 10 b.

Filter assembly 10 b includes a housing 11 b which defines an inlet 12 band an outlet 14 b. Dirty air 50 enters filter assembly 10 b via inlet12 b, and clean air 54 exits via outlet 14 b. The exterior of housing 11b includes mounting brackets 31 b, 32 b for positioning and securingfilter assembly 10 b in relation to surrounding equipment andstructures. A sensor receptor port 35 b is present on the exterior ofhousing 11 b to allow for connection of a sensor, as may be desired.Filter element 15 a is positioned within housing 11 b. In filterassembly 10 b of this embodiment, the filter element 15 a used is thesame as filter element 15 a of filter assembly 10 a of the firstembodiment. Also within housing 11 b is a noise suppression elementgenerally illustrated at 19 b.

Suppression element 19 b comprises a resonator 23 configured toattenuate sound at a peak of about 900 Hz. Detailed informationregarding resonators is provided above with respect to the firstembodiment of filter assembly 10 a. Resonator 23 has one end operativelyconnected in fluid communication with the outlet port 14 b of the filterassembly, and an opposite end to which is secured an annular mountingbracket 342. Mounting bracket 342 has a perforated central portionallowing air to pass therethrough into resonator 23, and defines anannular seal seat 343 that includes a cylindrical extension flange 345axially projecting away from resonator 23 in a direction toward inletport 12 b. The distal end of flange 345 is outwardly flared, for reasonswhich will be described below.

Filter assembly 10 b also includes an adsorbent element 310, shownenlarged in FIG. 13. Adsorbent element 310 comprises a cylindrical massof carbon 330 extending between first and second ends 330 a and 330 brespectively. Carbon element 330 is in the preferred embodiment ahollow, cylindrical extrusion of activated carbon held together by athermoplastic binder. Carbon element 330 can be produced, for example,by the teachings of U.S. Pat. Nos. 5,189,092 (Koslow), and 5,331,037(Koslow).

In some embodiments, the filter element, such as filter element 15 a,can be combined with an adsorbent element, such as adsorbent element310, into a single construction that provides both particulate andchemical filtration. For example, a particulate removal media can bepositioned around the external surface of carbon element 330. A filterelement that includes both particulate and chemical removal portions isdisclosed in U.S. Pat. No. 6,152,996 (Linnersten et al.).

The extruded cylindrical carbon configuration 330 of adsorbent element310 provides a solid surface for direct attachment of a sealing system340 thereto at end 330 a and an end cap 350 at end 330 b. Such “solid”carbon/binder extrusion also forms a unified adsorbent filter element310 that does not itself release any carbon or other particles orcontaminants into the filtered air stream.

End cap 350 is sealingly secured to end 330 b of carbon adsorbentelement 330. End cap 350 diverts air exiting filter element 15 a so thatthe air passes along the outer cylindrical surface of adsorbent 330 whenmounted as shown in FIG. 12 rather than moving directly, axially intothe central bore region of carbon adsorbent element 330. Air exitingfrom filter element 15 a impinges on a curved surface 355 of cap 350 andis rerouted from its “straight-line” flow from filter 15 a to a flowhaving a radial component. Surface 355 is an arcuately shaped surfaceradially extending from an axially aligned tip 352. Curved surface 355smoothly diverts the air with minimal resistance. Tip 352 is the centralpoint of exposed surface 355 of cap 350, although in some embodimentstip 352 may not be centrally positioned on cap 350. It will beappreciated that other surface configurations of end cap 350, such asflat or stepped surfaces, could be used. Referring to FIGS. 13 and 14,end cap 350 includes apertures 354 for passage of air therethrough andalong the outer surface of carbon element 330. Radial arms 356 defineand separate apertures 354 and provide structural support to cap 350.Additionally, some air may pass around the outer periphery of cap 350and between cap 350 and the interior of housing 11 b.

When adsorbent element 310 is operatively mounted as shown in FIG. 12,sealing system 340 provides an airtight seal at end 330 a betweenadsorbent element 310 and seal seat 343 and flange 345 of mountingbracket 342 (FIG. 12). The flared distal end of flange 345 helps guidesealing system 340 to seal seat 343. The formed seal, in combinationwith baffle 25 b and end cap 350, direct air flow through adsorbentelement 310, and, under normal conditions, prevent unintended levels ofair from passing through mounting bracket 342 and into resonator 23before the air has first passed through carbon element 330. With airflowing in the direction of from inlet 12 b to outlet 14 b, baffle 25 bforms a seal downstream from mounting bracket 342 and between the innersurface of the sidewalls of housing 11 b and resonator 23. End cap 350,baffle 25 b and sealing system 340 require all air flow from filterelement 15 a to pass through carbon adsorbent element 330 and throughmounting bracket 342 before passing on to the filter assembly outlet 14b.

Sealing system 340 is typically made from a flexible, compressiblematerial, such as polyurethane. The embodiment illustrated in FIG. 13shows sealing system 340 having a “stepped” configuration of decreasingoutermost dimension, which improves seating and sealing against sealingseat 343 and extension flange 345 of mounting bracket 342. Sealingsystem 340 directs air flow from filter element 15 a through carbonelement 330 before entering resonator 23.

In addition to managing air flow as described above, end cap 350provides structural support and anchoring of second end 330 b ofabsorbent element 310 to filter element 15 a by engaging with frame 200,specifically, with center 215 of frame 200 (see FIG. 5). Tip 352 isadapted for cooperative insertion into and retention by the recessedportion of center 215. The fit of tip 352 within frame 200 should holdadsorbent element 310 in axial alignment with filter element 15 a,although other features within the interior of housing 11 b may be usedto retain adsorbent element 310 in the desired position. Pressure in theaxial direction exerted by frame 200 on tip 352 operatively holdadsorbent element 310 in sealing engagement with sealing system 340against seal seat 343.

Each of sealing system 340 and cap 350 can be temporarily or permanentlyattached to carbon element 330. To provide a permanent attachment,sealing system 340 can be attached to carbon 330, for example, byadhesive, or by directly molding sealing system 340 onto carbon 330. Forpermanent attachment of cap 350, cap 350 can be, for example, adhesivelyattached to carbon 330. Cap 350 may include an annular recess to accepta portion of second end 330 b of carbon 330.

Adsorbent element 310 functions both as a chemical removal portion andas an element of sound suppression element 19 b. Adsorbent element 310is functionally similar to adsorbent element 300 of FIGS. 9 and 10 inthat it comprises adsorbent material for removing chemical contaminantsfrom the air passing therethrough or thereby. The volume between theinterior of housing 11 b and adsorbent element 310 can function as aresonator to suppress or attenuate sound. Additionally, carbon material330 of adsorbent element 310 directly adsorbs sound, thus providingindependent sound attenuation. In a preferred embodiment, adsorbentelement 310 is configured to attenuate a frequency peak of at leastabout 700 Hz, often greater than 700 Hz.

Other arrangements of adsorbent elements and adsorbent materials mayalso have both a chemical removal quality and a sound suppressionquality. Additionally, physical or particular filter elements, such asfilter element 15 a, may have some sound suppression qualities.

A Third Embodiment of a Filter Assembly

A third example of a filter assembly is shown in FIGS. 21-23 as a filterassembly 10 c. Filter assembly 10 c is adapted for use in a fuel celloperated vehicle, such as a passenger car, that uses a stack of PEM fuelcells providing an overall power output of 25 kW. It should beunderstood that filter assembly 10 c is specifically designed for suchan application, (i.e., a vehicle running on 25 kW), and that filterassemblies for other applications could be designed for thoseapplications that are different in size, shape and configuration,without departing from the overall features of filter assembly 10 c.

Filter assembly 10 c includes a generally cylindrical housing 11 c whichdefines an inlet 12 c and an outlet 14 c, shown in FIG. 22. Dirty airenters filter assembly 10 c via inlet 12 c, and clean air exits viaoutlet 14 c. A physical or particulate filter element 415 is positionedwithin housing 11 c. Filter element 415 is generally similar inconstruction to filter element 15 a of filter assembly 10 a of the firstembodiment, in that filter element 415 has cylindrically or spirallywound fluted filtering media 412 that provides straight-through airflow. An end frame 420 that includes a sealing system 460 is connectedto one end of filter element 415 for providing an air-tight, leak-freefit against housing 11 c. Positioned downstream of filter element 415 isan adsorbent element 430. Adsorbent element 430 can be any adsorbentmaterial described above, but is preferably a shaped adsorbent articlemade by, for example, a molding, a compression molding, or an extrusionprocess. Filter element 415 is similar to filter element 15 d of FIG. 10in that adsorbent element 430 is positioned between the particulatefiltering media 412 and end frame 420. Also within housing 11 c is anoise suppression element 19 c. In this embodiment, noise suppressionelement 19 c has a first resonator 421 and a second resonator 422, asdescribed in more detail below.

Housing 11 c can be made from any material that can provide the desiredelements, e.g., inlet 12 c, outlet 14 c, etc. Examples of usablematerials for housing 11 c include metals or polymeric materials, suchas epoxy, polycarbonate, polyethylene, and the like. Housing 11 c has atleast two separable sections, so that access can be gained to thecontained filter element 415 and other elements. The multiple sectionscan be held together by latches, clamps, straps, or other suitablesecuring mechanisms. In a preferred embodiment, inlet 12 c alsofunctions as a latch for retaining the multiple sections together. Theexterior of housing 11 c includes a mounting bracket 31 c, similar tobrackets 31 a, 31 b described above, for positioning and securing filterassembly 10 c in relation to surrounding equipment and structures.

Filter assembly 10 c differs from previously described filter assemblies10 a, 10 b in that the noise path through filter assembly 10 c differsfrom the air flow path. In each of filter assemblies 10 a, 10 b, thenoise follows a path that is the same but opposite in a direction fromthe air flow path. That is, the noise travels against the air passingthrough filter assemblies 10 a, 10 b. In this third embodiment, thenoise enters filter assembly 10 c through outlet 14 c and thenprogresses into and is attenuated by noise suppression element 19 c. Airflow enters filter assembly 10 c via inlet 12 c, passes through filterelement 415, adsorbent element 430, and exits through outlet 14 c. Thenormal air flow path does not pass through noise suppression element 19c, unlike in filter assemblies 10 a, 10 b where the air passes throughnoise suppression elements 19 a, 19 b, respectively.

Also, unlike filter assemblies 10 a, 10 b described above, filterassembly 10 c uses an arrangement where filter element 415 is unitarywith noise suppression element 19 c. By the term “unitary”, it is meantthat filter element 415 is essentially permanently attached or otherwiseconnected to noise suppression element 19 c, so that except formalicious or destructive acts, filter element 415 is not removable fromnoise suppression element 19 c. In the embodiment shown, filter element415 is constructed by winding layers of filtering media around noisesuppression element 19 c; noise suppression element 19 c functions as acore for filter element 415. The specific details of making filterelement 415 are those described above in relation to filter element 15a, except that the filtering media is wound around noise suppressionelement 19 c. Preferably, adsorbent element 430 is also unitary withfilter element 415 and noise suppression element 19 c. It is understoodthat in alternate designs, any of filter element 415, adsorbent element430 and noise suppression element 19 c can be removable from oneanother.

Noise suppression element 19 c includes first resonator 421 and secondresonator 422, seen in FIG. 23. Noise enters filter assembly 10 c viaoutlet 14 c (FIG. 22) and is attenuated by first resonator 421 andsecond resonator 422. First resonator 421 has a generally small volume,defined by an elongate tube with a fairly small diameter. Secondresonator 422 has a larger volume than first resonator 421 and isannularly and radially positioned surrounding first resonator 421.Second resonator 422 has a non-planar or non-flat first end 424 and anopposite non-planar or non-flat second end 425. Non-planar or non-flatends 424, 425 minimize echoes and better attenuate noise. In theparticular embodiment of second resonator 422, first end 424 is convex,in that it curves inward into resonator 422, and second end 425 isconcave, in that it curves away and out from resonator 422. First end424 includes a plurality of circumferentially spaced apertures 454 forpassage of sound waves therethrough. That is, apertures 454 act as aninlet for sound waves into second resonator 422. For first resonator421, a neck 451 acts as an inlet for sound waves into first resonator421.

The frequencies attenuated by resonators 421, 422 depend on variousdimensions, such as volume occupied, length, diameter, neck 451diameter, number of apertures 454, curvature of ends 424, 425, and soon. In this embodiment, first resonator 421 is constructed forattenuating higher frequencies than second resonator 422. Additionallyfirst resonator 421 attenuates a broader range of frequencies; that is,first resonator 421 has a broader attenuation range than that of secondresonator 422.

FIG. 25 graphically illustrates the levels and frequencies attenuated byfilter assembly 10 c, where first resonator 421 attenuates sound about apeak frequency of about 1000 Hz, and second resonator 422 attenuatessound about a peak frequency of about 540 Hz. The composite soundattenuation of the two resonators 421, 422 spans the fundamentalfrequency ranges of a typical twin-screw compressor. First resonator 421which is designed to resonate or attenuate a desired frequency, can alsofunction as a receptor for mounting on a spindle when winding filteringmedia onto second resonator 422, to make filter element 415. Thecombined resonator structure 19 c functions as a spool upon which theparticulate filter media is wound.

In the preferred embodiment shown, filter assembly 10 c, specificallyhousing 11 c, has a length no greater than about 500 mm, preferably nogreater than about 400 mm. Additionally, filter assembly 10 c, which isgenerally cylindrical, has a diameter no greater than about 300 mm,preferably no greater than about 260 mm. Specific characteristics of apreferred unitary filter element 415, adsorbent element 430, and noisesuppression element 19 c are illustrated in FIG. 24. As will beappreciated by those skilled in the art, the various dimensions offilter assembly 10 c, and the elements such as filter element 415,adsorbent element 430, and noise suppression element 19 c, are generallydependent on the volume allocated for occupation by filter assembly 10 cwithin the system with which the filter assembly will be used.

In the preferred embodiment for which the filter assembly 10 c wasdesigned, filter element 415 has a length “F” (“F prime”) no greaterthan about 240 mm, preferably no greater than about 200 mm. In thepreferred embodiment, “F” is no greater than about 191 mm. Of thisdistance, no greater than about 50 mm, preferably no greater than about20 mm is occupied by adsorbent element 430 as dimension “C”. In thepreferred embodiment, “C” is no greater than about 6.2 mm. Pleatedfiltering media 412, measured at “F_(M)”, occupies no greater than about200 mm, preferably no greater than about 180 mm. In the preferredembodiment, “F_(M)” is no greater than about 150 mm. The diameteroccupied by filter element 415, “D_(F)”, is generally no greater thanabout 290 mm, preferably no greater than about 270 mm. In the preferredembodiment, filter element 415 has a diameter “D_(F)” of about 230 mm.

For attaining the desired sound suppression characteristics of FIG. 25,noise suppression element 19 a occupies the majority of the diameter ofthe combined filter element 415, adsorbent element 430, and noisesuppression element 19 c within housing 11 c. In the embodiment shown inFIGS. 21 through 24, noise suppression element 19 c comprises firstresonator 421 and second resonator 422. First resonator 421 has adiameter “D_(R1)” at neck 451 of about 23 mm, and second resonator 422has a diameter “D_(R2)” of about 178 mm. Second resonator 422 has anoverall length “L_(R2)” of about 267 mm, with a portion of secondresonator 422 extending past filter element 415; second resonator 422extends distance “L′”, about 37 mm, past sealing system 460 of filterelement 415.

As will be appreciated by those skilled in the art, the specific volumeoccupied by first resonator 421 and second resonator 422 effects thesound attenuation characteristics of noise suppression element 19 c.Specifically, the lengths and diameters D_(R1) and D_(R2) of resonators421, 422 are a function of the desired sound attenuating properties ofthe resonator.

In typical specific embodiments of the combined filter element 415,adsorbent element 430, and noise suppression element 19 c, when noisesuppression element 19 c occupies about 50 to 90 percent of the diameterof the combined filter element 415, adsorbent element 430, and noisesuppression element 19 c, the cross-sectional area of the filter unit 10c occupied by noise suppression element 19 c is about 25 to 81 percent.Preferably, the diameter of noise suppression element 19 c is about 60to 80 percent of the total diameter, which represents only about 36 to64 percent of the total cross-sectional area. In the preferredembodiment, when noise suppression element 19 c has a diameter of about178 mm and filter element 415 has a diameter of about 230 mm, noisesuppression element 19 c occupies 77 percent of the diameter but only 60percent of the area.

Other combined arrangements of filter elements, adsorbent elements andnoise suppression elements may be useful in filter assemblies accordingto the present invention. It will be understood that the noisesuppression element can include any number of resonators. Also, asstated, the filter element, its housing, and/or adsorbent element (e.g.,carbon element) may produce sound attenuation. These combinedarrangements provide a single, removable and replaceable unit thatremoves particulate or physical contaminants, chemical contaminants, andalso provides sound attenuation or suppression.

Before continuing on with a discussion of a fourth embodiment of afilter assembly, the remaining components of equipment 101 of FIG. 1,including fuel cell 102, are described.

Fuel Cells

In FIG. 1, equipment 101, with which filter assembly 10 of the presentinvention operates, includes fuel cell 102. Fuel cells are deviceshaving two electrodes (an anode and a cathode) that sandwich anelectrolyte. The primary types of known fuel cell configurations arediscussed in the Background section of this specification. They all havethe common characteristics briefly discussed below, but vary inoperating temperatures and efficiency of operation. A hydrogen fuelsource is directed to the anode, where the hydrogen electrons are freed,leaving positively charged ions. The freed electrons travel through anexternal circuit to the cathode and, in the process, provide anelectrical current that can be used as a power source for externalelectrical circuits. The positively charged ions diffuse through thefuel cell electrolyte and to the cathode where the ions combine with theelectrons and oxygen to form water, a by-product of the process. Tospeed the cathodic reaction, a catalyst is often used. Examples ofcatalysts often used in the fuel cell reaction include nickel, platinum,palladium, cobalt, cesium, neodymium, and other rare earth metals.

The proton exchange membrane (PEM) type of fuel cell is a popular fuelcell configuration for use in powering vehicles due to its lowtemperature operation, high power density and ability to quickly varyits power output to meet shifts in power demand. The PEM fuel cell isoften simply referred to as a “low temperature fuel cell” because of itslow operation temperature, typically about 70 to 100° C., sometimes ashigh as 200° C. Fuel cell 102 of the preferred embodiments illustratedherein is preferably of the PEM, low temperature configuration. Hightemperature fuel cells are typically not as sensitive to chemicalcontamination due to their higher operating temperature. Hightemperature fuel cells are, however, sensitive to particulatecontamination, and some forms of chemical contamination, and thus hightemperature fuel cells may benefit from the filtering features asdescribed herein. Both types of fuel cells, low temperature and hightemperature, are usually used in combination with noisy equipment.

Various fuel cells are commercially available from, for example, BallardPower Systems, Inc. of Vancouver, Canada; International Fuel Cells, ofConnecticut; Proton Energy Systems, Inc. of Rocky Hill, Conn.; AmericanFuel Cell Corp. of Massachusetts; Siemans AG of Erlangen, Germany; SmartFuel Cell GmbH of Germany; General Motors of Detroit, Mich.; and ToyotaMotor Corporation of Japan.

Individual fuel cells, each having an anode, cathode, and electrolyte,are configured into “stacks” to provide the desired amount of externalpower. It will be recognized that the principles of this invention willbenefit the operation of generally any fuel cell configuration. Forexample, a typical passenger bus utilizes a fuel cell stack thatgenerates about 200 kW of power. A smaller vehicle, such as a passengercar, can utilize a fuel cell stack that generates about 25 kW of power.A small stationary electronic device can utilize a fuel cell stack thatgenerates 1 kW of power or less.

It will be recognized by one skilled in the art of fuel cells that theprinciples of the filter assemblies of this invention will benefit theoperation of generally any fuel cell and any fuel cell configuration.

The threshold levels of contaminants that are acceptable by various fuelcells are dependent on the design of the fuel cell. For example,hydrocarbons (methane and heavier), ammonia, sulfur dioxide, carbonmonoxide, silicones, and the like, are known to occupy space on thecatalyst and inactivate the sites to reaction. Thus, these contaminantsneed to be removed prior to their entering the reactive area of the fuelcell.

The exact level of contamination, and types of contaminants that areacceptable will vary depending on the catalyst used, the operatingconditions, and the catalytic process efficiency requirements. Thefilter assemblies of the present invention remove contaminants from theatmospheric air before the air is used in the fuel cell operation andapply to both low and high temperature operating fuel cell assemblies.

Compressors and Other Noise Making Equipment

As previously mentioned, equipment 101 also typically includes some airmoving equipment or air handling mechanisms that emanate noise (soundwaves), such as a compressor, fan, blower, or pump. This equipmentprovides the air (oxidizer) source to fuel cell 102. Unfortunately,moving parts such as rotors, impellers, lobes, vanes, pistons and othervarious parts of air moving equipment produce noise or sound waves. Inmany instances, the frequency of the sound waves produced spans 3 Hertzto 30,000 Hertz, sometimes as high as 50,000 Hertz, at levels of 85 to135 dB at one meter. While not all the noise emanating from the airmoving equipment is objectionable, the various assemblies of the presentdisclosure are directed to reducing the most objectionable portions ofthe noise profiles associated with an particular noise generatingportions of the system.

One common type of compressor 104 used in conjunction with fuel cell 102is a “Lysholm” twin screw compressor available from Opcon Autorotor ABof Sweden. This type of compressor typically has a noise output in therange of about 160 to 1100 Hertz, and at a level as high as 135 dB atone meter. Another common compressor is a “Roots blower” compressor.Other commonly used compressors include piston compressors, diaphragmcompressors, centrifugal compressors, and axial compressors. Everycompressor has a noise or frequency distribution associated with itsoperation. This distribution depends on the type of compressor and onvariants such as the input and output flow rates. For many compressors,the frequency distribution includes more than one frequency peak.

Compressors are available from, for example, Paxton Products ofCamarillo, Calif.; Pneumatec, Inc. of Kenosha, Wis.; Standard PneumaticProducts, Inc. of Newtown, Conn.; Vairex Corporation of Boulder, Colo.;and Honeywell Engines & Systems of Torrance, Calif. These compressorsgenerally have a large air mass flow, typically about 10 grams/second to400 grams/second.

Other air moving equipment that may be used with fuel cell 102 includes,for example, electric drive turbo chargers, compressor expanders, andthe like.

In an attempt to optimize the operation of fuel cell 102, the airentering fuel cell 102 may be humidified, often close to its saturationpoint. The high level of moisture is desired to minimize any chance ofthe electrolytic membrane of fuel cell 102 of drying out and beingincapable of carrying the charged ions. This humidification may occurupstream of compressor 104, downstream of filter assembly 10.Alternately, and possible preferably, this humidification may occurdownstream of compressor 104. Drier air may be more suitable for passingthrough compressor 104.

Compressor Discharge Apparatus

Even though a filter element, such as filter element 15 a, is presentupstream of compressor 104 to remove contaminants such as particles andchemicals, from the incoming air stream, contaminant matter may beintroduced to the air stream by the system itself, as for example, bycompressor 104. Besides generating noise, the fast spinning rotors,impellers, lobes, vanes or pistons of compressor 104 may discard minuteparticulate, either from being dislodged from a crevice or crease orother hidden corner, or from surfaces of the moving parts. One type ofcontaminant is molybdenum particles, which are caused by the coating onthe compressor internal parts weakening or being damaged duringoperation. The compressor unit 104 may also be a source of fluidcontaminants such as oils or greases that may leak through thecompressor or its seals and enter the air supply stream. Suchcontaminants, if allowed to enter the fuel cell stack, can prove to bevery harmful or detrimental to effective or efficient operation of fuelcell 102.

A compressor discharge apparatus or exhaust apparatus 103 is illustratedin phantom in FIG. 1. In some processes, it may be desired or bebeneficial to include a discharge apparatus such as apparatus 103downstream of compressor 104 or other air moving equipment for removalof compressor generated or other contaminants from the air supply streamand/or for further suppression of noise from the system. Apparatus 103can have, for example, a particulate filter, a chemical filter, a soundsuppressor, or any combination thereof. The specific configuration andarrangement of apparatus 103 can significantly vary with different fuelcells assembly configurations and will depend, for example, on thedesired efficiency of filter element 15 of filter assembly 10 for eitheror both particulate and chemical removal, and upon the requirements forthe suppression of sound by filter assembly 10. As stated above, somecompressors 104 may themselves contribute physical, chemical, or bothtypes of contaminants to the air stream, downstream of filter assembly10, which will need to be processed by an apparatus 103. Further, due tothe location of discharge apparatus 103 in the system (i.e., downstreamfrom compressor 104 and in closer proximity to fuel cell 102), the typeand nature of filtration and component materials that can be effectivelyused by apparatus 103 may significantly differ from those used by filterelement 15. Still further, apparatus 103 may include a humidifier thatincreases the moisture of the air passing therethrough. Additionally oralternatively, apparatus 103 may include a drain, floating check valve,or other device to remove excess water that has accumulated. Examples ofsuitable valve constructions are disclosed in U.S. Pat. Nos. 6,009,898(Risch et al.) and 6,209,559 (Risch et al.).

One embodiment of exhaust apparatus 103 is shown in FIGS. 15 and 16 asexhaust apparatus 103 a. Exhaust apparatus 103 a includes a housing 311a which defines an inlet 312 a and an outlet 314 a. Air from compressor104 enters exhaust apparatus 103 a via inlet 312 a, and exits via outlet314 a to fuel cell 102. The air from compressor 104 will typically be atan elevated temperature and pressure, such as, 370° F. to 400° F. andabout 3 atm. Because of these conditions, housing 311 a is preferably astainless steel alloy, such as 316 SS or 321 SS.

The embodiment of FIGS. 15 and 16 includes a sound suppression element319 a. Suppression element 319 a comprises a sonic choke 321 a and aresonator 322 a; each of sonic choke 321 a and resonator 322 a ispositioned within a chamber 332 a, 332 a, respectively. Chambers 331 a,332 a are defined by housing 311 a and baffle 335 a. Sonic choke 321 aand resonator 322 a can be designed to attenuate a desired peakfrequency or a range of frequencies. The sound present downstream ofcompressor 104 is generally the same, or at least similar to, the soundencountering filter assembly 10 upstream of compressor 104 except thatin the downstream case, both the air flow and the sound to be suppressedare flowing in the same direction. Detailed information regarding soundsuppression elements and resonators is provided above.

Another embodiment of exhaust apparatus 103 is shown in FIGS. 17 through20 as exhaust apparatus 103 b. Exhaust apparatus 103 b is similar toexhaust apparatus 103 a, in that exhaust apparatus 103 b includes ahousing 311 b defining an inlet 312 b and an outlet 314 b, with airentering via inlet 312 b and exiting via outlet 314 b. The embodiment ofFIGS. 17 through 20 further includes a sound suppression element 319 bthat comprises a resonator 322 b. Similar to exhaust apparatus 103 a,exhaust apparatus 103 b has two sound attenuation chambers 331 b, 332 bthat are defined by housing 311 b and separation baffle 335 b.

Exhaust element 103 b includes a filter element 315 for removingparticulate matter, oil, and ambient salts from the air passing throughexhaust element 103 b. Filter element 315 is resistant to the hightemperatures and pressure present within exhaust element 103 b. Oneexample of a filter element 315 includes an extension of pleated mediamounted between two end caps 315 a, 315 b. Preferably, perforated innerand outer liners or sleeves 316 a, 316 b, respectively, are positionedadjacent the media to provide support and protection to the media; suchsleeves or liners are well known. The sleeves, particularly the outersleeve, may be attached to housing 311 b, so that filter element 315 canbe slid into and out from the outer sleeve when filter element 315 isremoved from and replaced in exhaust assembly 130 b.

The filter media of filter element 315 should be able to withstand theconditions downstream of compressor 104, that of elevated temperatureand pressure, such as, 370° F. to 400° F. and about 3 atm, and often ofhigh levels of humidity or moisture. Examples of usable media for filterelement 315 include a polytetrafluoroethylene (PTFE) membrane carried byan aramid carrier (such as “Nomex” material), as is commerciallyavailable from Tetratec Corporation of Feasterville, Pa. It is desirableto use expanded PTFE membranes as they will not allow salts andpetroleum products such as oils to penetrate therethrough. U.S. Pat. No.6,123,751 (Nelson et al.), incorporated herein by reference, teaches thebenefits of PTFE. Another usable media is fiberglass media.

Filter element 315 may assume a number of physical shapes such as ovalor obround, similar to the shape of housing 311 b, or filter element 315may be circular. Planar filter panels may also be usable.

End cap 315 a is a “closed end cap” in that it extends across and coversthe end of the filter media such that no fluid flow access can be gainedto the inside of filter element 315 through end cap 315 a. End cap 315 ais essentially a cover over that end of filter element 315 that can beremoved as desired, for example, by removing an attachment mechanismsuch as hex nut 317. An o-ring 364 provides an air-tight seal betweenend cap 315 a and the exterior of the filter media, which may be theperforated outer sleeve or liner. Filter element 315 is removable andreplaceable from housing 311 b.

End cap 315 b is an “open end cap”; that is, open end cap 315 b includesa opening therein, preferably, centrally located. End cap 315 b, whichis typically a permanent feature of filter element 315, seats on seatsurface 370, specifically, on seal seat or ledge 373. An o-ring 374provides an air-tight seal between ledge 373 and end cap 315 b.

Combination Upstream Filter Assembly-Compressor-Exhaust Filter Assembly

An example of an embodiment of this invention that combines upstreamfilter and downstream exhaust filter assemblies in fluid communicationwith a compressor is illustrated in the air moving system 500 of FIGS.26-28. Air moving system 500 is adapted for use with a fuel celloperated system, as might be used with a remote traffic camera or avehicle radar detection system, that uses a stack of PEM fuel cellsproviding an overall power output of generally less than about 1 kW.Such lower power fuel cell applications require significantly lessamount of oxidant (e.g., air) than the larger power applicationspreviously described, and accordingly, these systems can utilize muchsmaller compressors or other air moving equipment; this in turnsignificantly reduces the overall size requirement of the filtrationportion of the assembly.

Air moving system 500 has an upstream filter assembly 501 that providesclean filtered air to a compressor 504. An exhaust filter assembly 503is located downstream of compressor 504 to remove any contaminants thatmay be introduced to the air stream by compressor 504 or that may nothave been removed by filter assembly 501 before the air stream isintroduced to a fuel cell. In this embodiment, compressor 504 is a smallvolume, vane compressor, providing an air flow rate of about 0.1grams/second to about 0.15 grams/second. The diameter of compressor 504is about 5 cm.

Referring to FIGS. 26 and 27, filter assembly 501 has a generallycylindrical housing 511 having a first end 511 a and an opposite secondend 511 b, the housing defining an inlet 512 and an outlet 514. Thediameter of housing 511 is similar to the diameter of compressor 504,about 5 cm. Dirty air enters filter assembly 501 via inlet 512, andclean air exits via outlet 514. Inlet 512 occupies an area essentiallythe same as the cross-sectional area of housing 511. Housing 511includes a bracket 523, which can be used to mount filter assembly 501as desired.

Extending across inlet 512 is a particulate screen 516, which removeslarge particles and contaminants and protects the below describedfiltration media. Screen 516 can remove leaves, debris, paper, and otherlarge contaminants. Positioned downstream of screen 516 is a particulatefiltration media 518. Media 518 can be any commonly used or suitablefiltration media, such as paper or cellulose, fiberglass, polymericscrim, and the like. Media 518 removes particulate contaminants,typically those about 0.01 micrometer and larger. Media 518 may includea surface layer or treatment, such as a polymeric nanofiber. Onepreferred surface layer for media 518 is a polymer blend of nyloncopolymer and waterproofing additive, which is described in U.S. Pat.No. 6,743,273 (which is incorporated herein by reference) and iscommercially available from Donaldson Company Inc. under the tradedesignation EON filtration media. Filtration media 518 extends acrossthe entire extent of inlet 512 and preferably forms a leak-free fitagainst housing 511, so that all air entering via inlet 512 must passthrough media 518.

Positioned downstream of media 518 is an adsorbent filtration element520. Adsorbent element 520 can be any adsorbent material describedabove, but in this embodiment, is a mass of carbon particles adheredtogether. Molded or extruded carbon materials, as described above, couldalternately be used as adsorbent element 520. Adsorbent element 520preferably extends across the entire cross-sectional area of housing 511to form a leak-free fit, so that all air passing through housing 511must pass through adsorbent element 520. Adsorbent element 520 may alsoprovide some degree of sound attenuation.

Downstream of adsorbent element 520 is positioned a scrim 522 forretaining adsorbent element 520. Scrim 522 inhibits loose carbonparticulates and other material from element 520 from escaping andpassing through to compressor 504. Also downstream of adsorbent element520 and downstream of scrim 522 is screen 526, which retainably supportsscrim 522 and adsorbent element 520 and media 518 between it and screen516.

Air, having entered via inlet 512 and passed through screen 516,filtration media 518, adsorbent element 520, scrim 522 and screen 526,exits via outlet 514. Outlet 514 is present in a volume 519, which issized and shaped to accept a portion of compressor 504 therein, theportion having the compressor inlet (not illustrated). In the embodimentillustrated, housing 511 includes a shoulder or other feature that actsas a stop for compressor 504. Compressor 504 may occupy the entirevolume 519, or a portion of volume 519 may remain empty. Any emptyportion of volume 519 may provide some amount of sound suppression ofsound waves emanating from compressor 504.

Housing 511 preferably forms a leak-free seal with compressor 504, sothat air that has passed through filter assembly 501 and outlet 514 thenpasses directly into and through compressor 504, and air that has notpassed through filter assembly 501 does not contaminate the interior ofcompressor 504. A rubber seal or any type of soft, compressible seal canbe used. Alternately or additionally, a snap-fit seal may be used. Fromthe inlet of compressor 504, air passes through compressor 504 and exitsthrough outlet 504 b. As mentioned above, the air flow rate throughcompressor 504 is about 0.1 grams/second to about 0.15 grams/second.Filter assembly 501, having a diameter of about 5 cm, is adequatelysized for such a flow rate.

Outlet 504 b is connected in direct fluid communication with the inletof exhaust filter assembly 503, illustrated in more detail in FIG. 28.Exhaust filter assembly 503 removes contaminants, such as metalparticles or lubricant mist, that may have been caused by compressor 504or that may have passed through filter assembly 501 upstream ofcompressor 504 without being removed.

Exhaust filter assembly 503 has a generally cylindrical housing 531defining inlet 532 and outlet 534. Inlet 532 and outlet 534, which areoffset from the center of housing 531, each has a diameter significantlysmaller than the diameter of housing 531. Air from compressor 504 entersexhaust filter assembly 503 via inlet 532, and cleaned air exits viaoutlet 534. Housing 531 includes a bracket 533, which can be used tomount exhaust filter assembly 503 as desired.

Downstream of inlet 532, and preferably extending the diameter ofhousing 531, is a screen 536, which retains particulate removal material540 in its prescribed volume. Screen 536 generally does not remove anyparticulate from the air stream, as the apertures are generallyadequately large to allow unobstructed flow there through. Particulate,and optionally liquid contaminants, are trapped by a removal material540. Removal material 540 can be any suitable filtration media or othermaterial suitable for removing the desired contaminants. Removalmaterial 540 extends across the entire extent of housing 531 andpreferably forms a leak-free fit against housing 531, so that all airentering via inlet 532 must pass through material 540.

In the embodiment shown in FIG. 28, removal material 540 comprises afirst depth loading material 542 and a second depth loading material544. An example of suitable depth loading materials is fiberglass in theform of a dense mat of fibers. Material 542 and material 544 may differfrom one another by the density of the mat, the size of the fibers, anyadditives or coating on the fibers, or by other properties.

Positioned downstream of removal material 540 is particulate filtrationmedia 548. Media 548 can be any commonly used or suitable filtrationmedia, such as paper, fiberglass, polymeric scrim, and the like. Media548 inhibits loose fibers or other material from removal material 540from escaping and passing through to the fuel cell positioned downstreamof assembly 500. One preferred media 548 comprises a polymer blend ofnylon copolymer and waterproofing additive, which is described in U.S.Pat. No. 6,743,273 and is commercially available from Donaldson CompanyInc. under the trade designation EON filtration media. Also downstreamof media 548 is screen 546, which provides support for media 548. Air,having passed through exhaust filter assembly 503 by passing throughremoval material 540 and media 548, exits via outlet 534 and progressesto the fuel cell downstream.

It is to be understood, however, that even though numerouscharacteristics and advantages of the present disclosure have been setforth in the foregoing description, together with details of thestructure and function of the disclosure, such disclosure isillustrative only, and is not intended to be limiting to the scope ofthe invention in any manner, other than by the appended claims. Theinvention is not to be limited to the described embodiments, or to usewith any particular type of fuel cell, or to the use of specificcomponents, configurations or materials described herein. Allalternative modifications and variations of the present invention whichfall within the broad scope of the appended claims are covered.

1. An air filtration assembly for use with a fuel cell and air movingequipment, the assembly comprising: (a) a first filter assemblycomprising: (i) an inlet and an outlet, the inlet configured to receivedirty air into the first filter assembly, and the outlet configured todeliver clean air from the first filter assembly; (ii) a particulatefilter constructed and arranged to remove particulate contaminants fromthe dirty air; and (iii) a chemical filter arranged to remove chemicalcontaminants from the dirty air; (b) air moving equipment having aninlet and an outlet and operable to move air from its inlet to itsoutlet, the inlet of the air moving equipment being connected to receiveair from the outlet of the first filter assembly; and (c) a fuel cellhaving an oxidant inlet connected to receive air from the outlet of theair moving equipment.
 2. The air filtration assembly according to claim1, further including: (a) a first housing comprising an interior and theinlet and the outlet of the first filter assembly, the particulatefilter and the chemical filter being positioned within the interior ofthe first housing.
 3. The air filtration assembly according to claim 1,further comprising: (d) a second filter assembly having an inlet and anoutlet, the inlet configured to receive air from the outlet of the airmoving equipment and the outlet configured to provide air to the fuelcell oxidant inlet, the second filter assembly comprising: (i) a secondparticulate filter constructed and arranged to remove particulatecontaminants from the air exiting from the air moving equipment.
 4. Theair filtration assembly according to claim 3: (a) the first filterassembly further including a first housing comprising an interior andthe inlet and the outlet of the first filter assembly, the particulatefilter and the chemical filter being positioned within the interior ofthe first housing; and (b) the second filter assembly further includinga second housing comprising an interior and the inlet and the outlet ofthe second filter assembly, the second particulate filter beingpositioned within the interior of the second housing.
 5. The airfiltration assembly according to claim 1, wherein the chemical filter ofthe first filter assembly comprises at least one adsorbent material. 6.The air filtration assembly according to claim 5, wherein the chemicalfilter comprises a first adsorbent material and a second adsorbentmaterial.
 7. The air filtration assembly according to claim 1, whereinthe particulate filter of the first filter assembly comprises acellulosic material.
 8. The air filtration assembly according to claim 7wherein the particulate filter of the first filter assembly isconfigured for straight-through flow.
 9. The air filtration assemblyaccording to claim 1, the first filter assembly providing soundsuppression.
 10. The air filtration assembly according to claim 9, thefirst filter assembly including: (a) a first housing comprising aninterior and the inlet and the outlet of the first filter assembly, theparticulate filter and the chemical filter being positioned within theinterior of the first housing, wherein the first housing provides soundsuppression.
 11. The air filtration assembly according to claim 1,wherein the air moving equipment is a compressor.
 12. An air filtrationassembly for use with a fuel cell and air moving equipment, the assemblycomprising: (a) a filter assembly comprising: (i) an inlet and anoutlet, the inlet configured to receive dirty air into the first filterassembly, and the outlet configured to deliver clean air from the firstfilter assembly; (ii) a particulate filter constructed and arranged toremove particulate contaminants from the dirty air; and (iii) a chemicalfilter arranged to remove chemical contaminants from the dirty air, thechemical filter comprising an immobilized carbon element; (b) air movingequipment having an inlet and an outlet and operable to move air fromits inlet to its outlet, the inlet of the air moving equipment beingconnected to receive air from the outlet of the first filter assembly;and (c) a fuel cell having an oxidant inlet connected to receive airfrom the outlet of the air moving equipment.
 13. The air filtrationassembly according to claim 12, wherein the chemical filter comprises aplurality of immobilized carbon elements.
 14. The air filtrationassembly according to claim 12, wherein the chemical filter furthercomprises a fiber element.
 15. The air filtration assembly according toclaim 14, wherein the fiber element comprises acidic material.
 16. Theair filtration assembly according to claim 14, wherein the fiber elementcomprises basic material.